There is a trend in current plate and Steckel mills for the rolling of shorter feed stock such as short (usually thick) slabs or ingots. Typically, feed stock has been of the order of 3 to 4 meters or longer in length, but now there is a requirement to roll feed stock that is only of the order of 2 to 3 meters or less in length. This is particularly applicable in the case of plate mills rolling products from thick slabs or ingots and Steckel mills rolling ‘exotic’ materials e.g. titanium and nickel grades. These short slabs or ingots pose a particular problem with the operation of the edger.
Rolling mill edgers are used to maintain a required width of the slab as it is processed. The edgers typically comprise work rolls mounted at either side of a centerline on a section of a path over which the feed stock is moved in its various forms, for convenience referred to as a slab, but encompassing other forms from feedstock to finished product. The work roll separation is adjustable according to the plate width required. Idler rolls extend across the center part of the path, mounted with their roll axis perpendicular to and in the same plane as the centerline. Feed rolls are provided across a substantial part of the full width of the path ahead of or beyond the edger section of the path and these feed rolls are typically driven directly from motors via drive shafts, or sometimes using a gearbox. However, in the edger section of the path, between the edger work rolls, there are usually only idler rolls. This is not a problem if the slabs are of a conventional length as at least a part of the slab is always resting on driven rolls in the path outside the edger section. However, for short slabs, there may be a time in the rolling cycle when no part of the slab is on a driven roller and the slabs get stuck. Replacing the idler rollers with driven rollers in the section between the edger work rolls has the disadvantage that edger work roll changes are made more complicated because of the need to remove the driven rollers in that section to allow access for a roll change. Unlike the existing idler rollers, driven rollers cannot be simply lifted out, but would have to be disconnected from their gear and drive mechanism. JPS5671503 describes rolling equipment which can roll both plate and hot coil by providing an intermediate roller table which is raised into position for plate rolling. JPS6138706 describes an edging mill provided with a pair of non-driven edging rolls which are movable in the sheet width direction, to reduce the cost and space requirements associated with driven rolls.